Presentation on theme: "Cardiac and Smooth Muscle Chrissy Benson. Cardiac Muscle cardiocytes=cardiac muscle cells 10-20µm in diameter; 50-100µm in length Single nucleus Myofibrils."— Presentation transcript:
Cardiac and Smooth Muscle Chrissy Benson
Cardiac Muscle cardiocytes=cardiac muscle cells 10-20µm in diameter; µm in length Single nucleus Myofibrils and accessory muscle contraction proteins ~ to those in skeletal muscle Most of these are encoded by genes specifically expressed in cardiocytes.
Contractile cells -pump heart - Do not initiate their own AP Autorhythmic cells –Do not contract –Initiate and conduct APs –No resting potential; neural input not necessary to initiate an AP –Pacemaker activity instead: Slow depolarization, drift to threshold, then firing
Myofilaments of the cells are not parallel as they are in skeletal and cardiac muscle Symmetrical patterns of thick and thin filaments not evident No troponin complex
contracts in all directions, not just linearly more force/cross sectional area (fewer other organelles)
Smooth Muscle activation –autonomic nervous system, varicosities and receptors all over cell –hormones like nor epinephrine released from neurons or in the blood –connected in sheets with gap junctions so contractions can spread into neighboring cells –can also be stretch activated (uterus) or spontaneously activated (gut)
Smooth Muscle excitation/contraction –activated by opening calcium channels on the cells surface, influx of extra- cellular calcium (small, thin cells, slow) –calcium activates myosin and frees up actin (no tryptomyosin)
Cardiac Muscle Disorders Dilated Cardiomyopathy -will not limit quality/duration of life –risk of sudden death heart enlarges, functions poorly muscle becomes weak, and unable to pump blood efficiently causing fluid build up in the lungs, and results in a feeling of breathlessness: called left heart failure. right heart failure causes fluid build up in the tissues and organs of the body (ie. legs, ankles, liver, and abdomen)
Cardiac Muscle Disorders
Symptoms: Shortness of breath Swelling of the ankles Tiredness Palpitations and Syncope Chest pain Causes: Viral Infection Auto-Immune Disease Excessive alcohol consumption/exposure to toxic compounds Pregnancy Familial disease
Cardiac Muscle Disorders Hypertrophic Cardiomyopathy -thickening of muscle; may thicken in normal individuals as a result of high blood pressure or prolonged athletic training. In this case, thickening occurs without an obvious cause -normal alignment of muscle cells is absent and this abnormality; called myocardial disarray
Cardiac Muscle Disorders
Symptoms: Shortness of breath Chest pain Palpitation Light-headedness and blackouts Causes: Dominant mutation myosin, troponin T, alpha tropomyosin, cardiac myosin binding protein-C, or the essential and regulatory light chains. important proteins for the contraction of the heart.
References.. Pasternak, Jack J. An Introduction to Human Molecular Genetics Mechanisms of Inherited Diseases. 2 nd Edition pp. 373;